Joysticks are conventionally utilized to provide positioning information in a single or a two-dimensional system. For example, joysticks are commonly used to position objects on the screen of a video game or to manipulate a machining tool about a two-dimensional work surface.
The typical joystick such as that shown in U.S. Pat. No. 4,375,631, issued on Mar. 1, 1983, to Thomas R. Goldberg, consists of two potentiometers coupled to a control handle. As the handle is pivoted about two orthogonal axes, the resistance of the potentiometers vary in relation to the position of the handle. The value of the resistance or the magnitude of the current passing through the potentiometer indicates the position of the joystick handle about the corresponding axis. This resistance, or current, representing the handle's position is then utilized to control some other function such as the position of the video game object or the machine tool head. The movement of the handle may be used to dynamically control the object by a circuit which continuously monitors the change in the potentiometer resistance and employs the monitored resistance to move the object in a pattern corresponding to the movement of the joystick handle.
In an alternative joystick embodiment, the movement of the handle produces a pulsed electrical signal in which the frequency of the pulses represents the position of the handle along one orthogonal axis. The benefit of this latter type of joystick is that the signal produced by the movement of the handle is digital in nature and can readily be handled by digital computer circuits, as opposed to a conventional potentiometer based device producing an analog output signal which has to be digitized for processing. The present invention employs this latter or digital approach.